#include <stdio.h>

#include <pthread.h>

#include <curl/curl.h>

#define NUMT 4

/* we have this global to let the callback get easy access to it */

static pthread_mutex_t *lockarray;

#ifdef USE_OPENSSL

#include <openssl/crypto.h>

static void lock_callback(int mode, int type, char *file, int line)

{

(void)file;

(void)line;

if(mode & CRYPTO_LOCK) {

pthread_mutex_lock(&(lockarray[type]));

}

else {

pthread_mutex_unlock(&(lockarray[type]));

}

}

static unsigned long thread_id(void)

{

unsigned long ret;

ret = (unsigned long)pthread_self();

return ret;

}

static void init_locks(void)

{

  int i;

  printf("crypto num is %d\r\n", CRYPTO_num_locks());

  lockarray = (pthread_mutex_t *)OPENSSL_malloc(CRYPTO_num_locks() *

  sizeof(pthread_mutex_t));

  for(i = 0; i<CRYPTO_num_locks(); i++) {

  pthread_mutex_init(&(lockarray[i]), NULL);

}

CRYPTO_set_id_callback((unsigned long (*)())thread_id);

CRYPTO_set_locking_callback((void (*)())lock_callback);

}

static void kill_locks(void)

{

  int i;

  CRYPTO_set_locking_callback(NULL);

  for(i = 0; i<CRYPTO_num_locks(); i++)

    pthread_mutex_destroy(&(lockarray[i]));

  OPENSSL_free(lockarray);

}

/* List of URLs to fetch.*/

const char * const urls[]= {

  "https://www.example.com/",

  "https://www2.example.com/",

  "https://www3.example.com/",

  "https://www4.example.com/",

};

static void *pull_one_url(void *url)

{

  CURL *curl;

  curl = curl_easy_init();//每个线程初始化一个句柄，绝对不能混用。

  curl_easy_setopt(curl, CURLOPT_URL, url);

  /* this example doesn't verify the server's certificate, which means we

     might be downloading stuff from an impostor */

  curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);

  curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0L);

  curl_easy_perform(curl); /* ignores error */

  curl_easy_cleanup(curl);

  return NULL;

}

int main(int argc, char **argv)

{

  pthread_t tid[NUMT];

  int i;

  (void)argc; /* we don't use any arguments in this example */

  (void)argv;

  /* Must initialize libcurl before any threads are started */

  curl_global_init(CURL_GLOBAL_ALL);

  init_locks();//初始化openssl的回调函数，加载线程锁

  for(i = 0; i< NUMT; i++) {

    int error = pthread_create(&tid[i],

                               NULL, /* default attributes please */

                               pull_one_url,

                               (void *)urls[i]);

    if(0 != error)

      fprintf(stderr, "Couldn't run thread number %d, errno %d\n", i, error);

    else

      fprintf(stderr, "Thread %d, gets %s\n", i, urls[i]);

  }

  /* now wait for all threads to terminate */

  for(i = 0; i< NUMT; i++) {

    pthread_join(tid[i], NULL);

    fprintf(stderr, "Thread %d terminated\n", i);

  }

  kill_locks();//销毁openssl线程锁

  return 0;

}